Patients with chronic obstructive pulmonary disease (COPD) have limited functional ability largely due to their inability to tolerate exercise and manage their activities of daily living. In the absence of a pharmacological cure for COPD, nursing studies on inspiratory muscle training (IMT) have shown promising results but it remains unclear which patients will benefit the most from IMT. This study will determine which patients (mild, moderate, or severe) will benefit the most from IMT. At two clinical sites in Chicago and California with a double blind experimental design, the effects of 6 months of IMT will be examined in a total of 90 patients with mild, moderate, and severe COPD. Patients will be randomly assigned to either a dynamic exercise group or a control group with sham treatment. Patients' response to IMT will be assessed with respect to clinical, psychosocial and physiological variables. These include: clinical symptoms (by Bronchitis Emphysema Checklist and daily log); general exercise performance (by 12 minute distance walk); functional ability (Sickness Impact Profile); psychosocial adjustment to illness (PAIS by Derogatis); respiratory muscle strength (Maximal Inspiratory and Expiratory Pressures); and respiratory muscle endurance (sustained inspiratory pressure endurance time). Pulmonary function tests incuding lung volumes and nutritional status will also be measured to determine their effects on the outcomes of IMT. A terminal interview will be done to identify patients' perceptions of the benefits of IMT. All subjects will receive weekly telephone calls to increase compliance. Data will be analyzed using analysis of variance with repeated measures; descriptive and coorrelational statistics; and qualitative techniques adapted from Lofland and Lofland (1984). Knowledge gained from this study will help nurses and physicians decide at what stage of COPD (i.e. mild, moderate, severe) the IMT should begin to benefit the patients most; and predict which aspects of functional status will improve.